Machine tool



Aug- 1, 1939- A. oBRHoFI-KEN 2,157,673

MACHINE TOOL Filed Jan. l5, 1936 6 Sheets-Sheet l a@ wf m C42/Xander Obama/6(6)? C/TTOQrgQ/s Aug. 1, 1939. AV. oBERHoFFKx-:N 2,157,673

MACHINE TOOL Filed Jan. 13, 1956 6 Sheets-Sheet 2 NVE mom, (l/exam der Ober/70% /37 fm] my, 4 j UITTOQUQS Aug. 1, 1939. A. oBERHoFl-'KEN MACHINE TOOL Filed Jan. 13, 1936 6 Sheets-Sheet 5 /IllllIll/IIIIIIIIA \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\m\w\\\\\\\mm\\m\\\\ ,S www #in 0.0Mu Ka MF O. r w w. d f N NQ mw X00 W@ Aug. 1, 1939. A. OBERHOFFKEN 2,157,673

MACHINE TOOL Filed Jan. 15, 1956 6 Sheets-Sheet 4 Aug. l, 1939. A. OBERHOFFKEN MACHINE TOOL Filed Jan. 15, 1936 6 Sheets-Sheet 5 N vf; N To Q @Wega/mer Oberhof/,Wen

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A. OBERHOFFKEN mamma TooL Filed Jan. 1:5, 195e 6 Sheets-Sheet 6 NVE NTO@ CL4/@Xander Oberhof/wz? Patented Aug. l, 1939 UNITED STATESAVA 'PATENT OFFICE MACHINE TOOL Application January 13, 1936, Serial No. 58,854

Claims.

This invention relates to general purpose machine tools for performing various metal-removing operations such as drilling, milling, tapping, boring, reaming, etc., and has more particular 5 reference to the construction and mounting of and at different lines of approach without necessitating costly changes in bed structure. i

A more detailed object is to provide a machine tool having a slidable tool head demountably supi ported directly from the frame of the xture in' which the work piece is held While being operated upon.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which- Figure 1 is a. fragmentary vertical sectional View of a machine tool embodying the features of the present invention.

Fig. 2 is a fragmentary perspective view of a machine shown in Fig. 1.

Figs. 3 and 4 are vertical transverse sectional views of the self-contained tool heads shown in Figs. 1, 2 and 4, the sections being taken respectively along the lines 3--3 and 4-4 of Fig. 5.

' Figs 5 and 6 are sectional views taken respectively along the lines 5-5 and 6-6 of Fig. 4.

Figs. 7 and 8 are sectional views taken along the lines I-1 and 8 8 of Fig. 6.

Fig. 9 is a schematic view and wiring diagram.

Fig. 10 is a sectional view taken along the line III-I0 of Fig. '1.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will herein describe indetail the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to theY specific form disclosed, -but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims, f

The machine tools shown in the drawings to illustrate the invention comprise generally a base or pedestal I upon which is supported a xture 2 in which a work piece 3 may be held accurately in elevated working position above the floor while being operated upon by one or more tools 4 on a spindle 5 rotated and reciprocated axially by a self-contained power unit 6. The fixture frame is a rigid box-like structure removably secured as by screws to the base I and having upright side walls 1 and 8 rigidly joined at their upper ends by a top wall 9 and having an opening I0 through which the work piece may be slid into operating position in which it is pressed against locating plates II by the action of clamping cams I2. In the forms shown in Figs. l and 2, the tool spindle projects through an opening Ia and is guided at its projecting end in a bushing I3 on the xture. The other end is journaled in a gear housing I4 detachably secured to an attachment surface I4a on the forward end wall of a box-like casing I5 of the power unit 6.

To avoid the necessity of providing the usual special bed mounting for the tool feeding and driving mechanism and to enable the line of approach ofthe tool to the work to be changed at minimum expense, the unit 6 is, in the present instance, supported solely from the fixture frame 2. For this purpose, a bracket IB is detachably bolted to the side wall 'I and has a boss I'I which is apertured to receive the ends of spaced parallel rods I8 having machined external surfaces forming the guideways for the tool head. The rods are anchored in the boss I'I and project from the xture at the angle necessary for deiining the desired line of tool approach.

To support the head 6 from the rods I8, opposite side walls of the casing I5 are formed with attachment surfaces 20 to which are bolted flanges 2I of elongated tubular brackets 22 which are slidable on the rods I8 and have internal Way surfaces mating properly with the guide surfaces on the rods. If desired, a tongue and groove connection 23 may be provided between the casing walls I9 and the brackets 22. The casing I5 is thus arranged to slide back and forth along the rods, and if desired may be removed as a unit simply by detaching the brackets 22. A stop collar 24 on one of the rods determines the limit position to which the head may be retracted.

With the mounting described above, it will be observed that the tool head is supported entirely from the fixture frame thereby avoiding the necessity of providing a special bed structure for supporting the tool head guides. While the head overhangs the point of attachment of the rods to the rigid iixture frame and is primarily supported by the latter through the medium of the rods, this does not detract from the accuracy of the guiding action t'o an objectionable degree, for in most instances tool guides, such as those indicated at I3 (Fig. 1),Vwill be employed. Also, when the tool is in actual engagement with .the work,vthe head will be disposed close to the supporting bracket I6. By thus mounting the tool head, the machine tool may be adapted readily and economically to changes in the design or character of the work piece to be operated upon. For example, to change the position or line of tool approach, it is merely necessary to change the position of the bracket I6 or construct a new bracket for supporting the bars I 3 at the proper angle, no changes in the bed structure being required.

All of the machine -tool functions which involve power driven or moving parts are performed including driving of the tools and effecting relative feed and rapid traverse motions in automatically defined cycles by mechanism housed within the casing I5 and arranged in a novel manner to obtain a high degree of compactness and to enable the different groups of operating parts -to be removed as individual units for purposes of repair. To this latter end, the casing comprises a central casting, front and rear top cover plates 35 and 36, and a rear cover 31 having an end plate 38 thereon.

Power for driving the tool spindle and for moving the head in both directions at feed and rapid traverse rates is derived from a combined feed and -tool driving motor 40 (Fig. 5)` and a rapid traverse motor 4I. 'I'he stator 42 of the feed motor is received in a cylindrical recess 43 within the casting I5 and may be removed therefrom after removal of the rear cover 31 and a set screw 44 by which the stator is held in place. The rear end of the motor shaft 45 carries a fan 46 for inducing air circulation laterally through the casing and is journaled in bearings 41 and 48. 'I'he forward end of the shaft projects through a wall 43 and carries an element 50 of a coupling for extending the motor drive to gearing within the box I4 for reducing the speed to the value a which the tool spindle 5 is tobe driven.

'I'he rapid traverse motor 4I is associated with a fnction brake indicated generally at 5I and the two constitute a sub-assembly mounted within a cylindrical bore in the lower part of the vcasing I5 and removable as a unit therefrom after. the rear cover 31 and other parts have been removed and a set screw 52 loosened. To provide for a high degree of compactness of the operating parts within the casing I5, the motor shaft comprises a tube 53 journaled at its forward end in a bearing 54 and at its rear end in a bearing 55 in a plug 56 which threads into the rear end of a tube 51 received in a rearwardly opening recess in the casing I5. Thev brake comprises nonrotatable disks 59 splined within the tube 51 and normally urged by springs 60 into gripping engagement with rotatable disks 6I carried by the rotor shaft 53. The stator 62 of the motor is carried by a tube 63 supported by bearings 64 for a limited degree of angular movement within the tube 51 under .the reaction exerted by the load on the motor when the latter is started. Inthis movement, the brake is released against the action of the springs by a cam mechanism 65.

Preferably, the rotary motions of the feed and rapid .traverse motors are combined by diiferential gearing 66 and applied to a rotary feed element in the form of a nut 61 projecting through the forward end of the casing I5 and with the motor shaft 53. Studs 1I carried by the nut support planet gears 1I meshing with the sun gear` teeth 12 cut on the end of the rotor shaft 53 and with internal teeth on a ring gear 13 which also constitutes a worm wheel .meshing with a worm 14 (Figs. 3 and 5) on a cross shaft 15 v,rotatably supported fromopposite side walls of the casing I5 Rotary power from the shaft 45 of the feed motor is communicated to the worm shaft 15 through a vertical shaft 16 (Fig. 3) connected at its lower end to the motor shaft by spiral gearing 11 and a second vertical shaft 13 carrying at its lower end a bevel pinion 13 which meshes with the bevel gear 8l fast on the worm shaft 15. The upper splined ends of the shaft 16 and 1l project into the casing cover 35 and carry intermeshing pick-off gears 13 and 3l which may be removed and changed as desired in order to obtain the desired feed rate. v

The nut 61 may be rotated by either of the motors 40 and 4I causing the head 6 to be advanced along the screw 6! in a direction and at a speed corresponding to -that `of the operating motor. In the event that the feed motor 4l is operated simultaneously with the rapid traverse motor, the rate of motion of the head will be increased or decreased accordingly. When the feed motor alone is operating, the shaft of the rapid traverse motor is held against rotation by the brake 5I which is released automatically as an incident to starting of the rapid traverse mol tor. i To enable the head 6 to be advanced manually, the pick-off gear 8|! is rotatable on a sleeve .I splined on the shaft 13 and carrying a tooth 32 which, in the lower position of the sleeve shown in Fig. 7, enters a notch in the hub 53 of the gear thereby providing a driving connection between the shaft and the gear. By turning an external handle 84 (Fig 6) a rock shaft l5 may be oscillated whereupon an arm 86 thereon engaging a collar on the upper end of the sleeve II will raise the latter to disconnect the shaft 13 and the gear 80. Thereafter, the shaft may be turned manually through the medium of a crank (not shown) inserted through an opening l1 in the cover 35 and engaging a coupling element 3l on the upper end of the shaft.

In the present instance, all of the switches, relays, overload devices, and the means for actuating the switches to control the selective operation of the motors 4l and 4I and thereby define automatic cycles of movements of the tool head, are incorporated in the unit 6 and movable therewith. The switching mechanism and its actuating means constitute a separate readily detachable sub-assembly carried beneath the top and reary covers 36 and 31 and including a frame 63 fitting on and fastened by screws to the casting l5. The cover 3 is secured to the sub-frame Il by screws 3| (Fig. 5). Y

Rotatably supported in bearings 32 on the frame 69 is a cam shaft 93 having fast thereon pairs of cams 34, 95, I6. 31 and camsv 5l and 33 76 respectively operating switches 94s to 99l which are arranged in staggered relation as shown in Fig. 6 on opposite sides of the cam shaft. Each switch comprises a pair of movable contacts |00 (Fig. '1) urged by a spring |0| into engagement with stationary contacts |02 and adapted to be moved to switch-open position by upward movementof an insulating pin |03 against the lower end of which bears a bell crank lever |04 pivoted at |05. An arm |06 of the lever constitutes the follower of one of the cams. The followers of the adjacent cams project in opposite directions as shown in Fig. 6.

The cam shaft is advanced unidirectionally with a step-by-step movement effected by a timing element comprising a disk |09 on the periphery of which the dogs ||0, |I| and ||2 are mounted for circumferential adjustment. The

disk, which'is rotatably supported by a bearing 3 on the projecting end of the plug 56 (Fig. 5), constitutes the ring gear of a planetary gearing having planet gears ||5 meshing with the internal teeth of the ring gear and with teeth I||i cut on the rear end of a tubular shaft I|1 encircling the screw 09. This shaft is coupled at its forward end to the rear end of the nut 61 for rotation therewith and at its rear end is journaled in a bearing ||8.

The planet gears ||5 also mesh with internal teeth I |9 on a stationary flange I 20 and of a number one less than the number on the disk |09. By virtue of this arrangement, the disk will rotate through a distance equal to the pitch of its teeth for each revolution of the nut 61. The dog disk thus turns in unison with the movements of the tool head but at slower speed than the nut. By employing the planetary speed reducing mechanism driven from the shaft extended through the rapid traverse motor shaft, the space required for the disk-driving parts is reduced to a minimum, and a maximum travel of the tool head may be obtained within one revolution of the dog disk.

The dogs operate as cams upon a follower roller |2| rotatably supported on the lower end of a plunger |22 slidable vertically in a guideway formed by the sub-frame 09 and a U-shaped plate |23 fastened thereto. Pivoted at |24 on the plunger is a pawl |25 engaging elongated teeth of a ratchet wheel |25 on the cam shaft 93. The pawl is urged toward the ratchet teeth by a spring |21 which also urges a detent |28 into engagement with the ratchet teeth so that the cam shaft 93 will, after being advanced a predetermined distance by the action of the pawl |25, be cammed quickly through the remainder of its step and there retained in xed position by the detent |28. It is during this rapid advance of the cam shaft that the cams thereon operate to change the positions of the control switches.

From the foregoing, it will be seen that the cam shaft, the switches, the ratchet drive, and the dogs are accessible after removal of the covers 38, 31 and 38, and that the entire switch, cam shaft and ratchet assembly may be removed by detachment of the sub-frame 89 from the casing I5. The cover 31 also provides spaces on opposite sides of the ratchet pawl in which spaces, relays |29 and |30 are disposed (Figs. 4 and 9). Overload release devices I3| are housed within the rear end of the top cover 36 and disposed on opposite sides of the cam shaft 93. These may be reset by depressing a button |32 (Figs. 4 and 5) in the cover 36.

In the present instance, the cam actuated switches operate directly and at normal line voltage to control the starting, stopping and direction of rotation of the motors 40 and 4|, the magnetic relay |29 servingto govern thc flow of current from power lines L1, L2 and L3 to the switches and having a winding controlled by start and stop push button switches |32 and |33 which may be mounted at a convenient point on the casing I5. The power lines extend through a flexible armor into a terminal box |9| on the cover 31 within which the line terminals bear against contact terminals |92 leading to the control switches as shown in Fig. 9. The relay |30 is employed to enable several of the power units to be controlled `in multiple from remotely located start and stop push button switches |34 and |35.

Assuming that the motor and control circuits are arranged as shown in Fig. 9, a cycle of rapid approach, feed and rapid return motions will be executed as follows in response to the closure of the start switch |32 with the parts positioned as shown in Fig. 13. Closure of this switch completes a circuit for energizing the winding of the relay |29 extending from the power line L3 through a conductor |36, the closed switch |35, a conductor |31, the overload switch, the switch 98* which is held closed by the cam 98, the switches |33 and |32, a conductor |38, the winding of the relay, and a conductor |39 leading to the power line L2. Energization of the relay closes a switch |40 in parallel with the manually operable switch |32 which thereafter may be allowed to open. Energization of the relay also closes switches |4| thereby applying current to the motors 40 and 4I through the switches 95"L and 91 which, in the starting position of the tool head, are held closed by their cams and 91. By the combined action of these motors, the head is advanced at a rapid traverse rate and the dog disk |09 rotated at a corresponding but slower speed,

When the dog engages and actuates t'ne follower |2|, the cam shaft 93 is advanced one step whereupon the switches 95a are opened thereby interrupting the rapid approach motion, the forward movement of the tool head being continued at the feed rate by the motor 40. After the tools have operated upon the work, the dog I2 will actuate the ratchet pawl causing the cam shaft to be advanced through another step during the rapid movement of which the cams 94 will close the switches 94a thereby initiating rotation of the rapid traverse motor in a direction to retract the tool head. In the most advanced position of the tool head, the roller |2| engages the surface/H2 so that the cam shaft is not advanced in the initial part of the rapid return motion. The condition of the switches is not changed as the dog passes the follower |2| so that the rapid return motion continues until the dog ||0 has actuated the ratchet mechanism to advance the cam shaft in its fourth and final step of movement during which the cam 98 opens the switch 90a momentarily thereby deenergizing the relay |29 and stopping both of the motors. In this same movement of the cam shaft, the switches 95n and 91a are closed by their cams to condition the circuits for the next cycle. When the movement of the tool head is arrested, the roller |2| is in engagement with the surface H0 on the d og ||0. During any part of the cycling, the movement of the head may be interrupted by opening either of the stop switches |33 and |35. Thereafter the cycle may be continued by closing one of the switches |32 and |34.

To permit the control mechanism to be conditioned quickly and conveniently for the periormance of other types of automatic cycles, such for example as that employed for tapping operations, the cam shaft 93 is equipped with one or more auxiliary sets of cams 94b to 99b which may be brought into operative association with the respective followers |04 by shifting the cam shaft axially through the medium of a knob |50 on the projecting end of the cam shaft. To release the cam shaft for such shifting, a knob |5| is actuated to withdraw a latch |52 out of a groove |53 in which the latch is seated to lock the cam shaft with the desired set of cams in operative association with the switch actuating followers |04.

The power unit described above is adapted for spot facing operations wherein the head is advanced against a positive stop where it dwells for a. brief interval while the tool is performing the facing operation. The stop may take the form of an adjustable screwthreading into the bracket |6 with its head positioned for engagement with the forward end of the tool head after the tool has advanced to the proper depth. When such engagement occurs, further rotation of the nut 61 is prevented, and the increased torque applied to the brake 5| by the feed motor acting through the differential gearing causes slippage of the brake and continued rotation of the tool spindle.

Mechanism is provided for timing the duration of the dwell period and automatically initiating rapid return of the tool head to starting position. This mechanism comprises generally means which is rendered operative automatically by the action of the dog ||2 as the head approaches the stop |55 and which operates to latch the rapid return switches 94 against closing at the normal time above described and permitting such closure after the lapse of an interval timed by the rotation of the feed motor 40.

Referring now to Figs. 5, 6 and '1, the followers |04 for the rapid return switch cams 94 are equipped with tails |56 which, when these followers are moved by their cams, are raised above Aa shoulder |51 on an elongated latch |58 pivoted at |59 on the frame 09 and urged toward the followers by a torsion spring |60. With their followers thus latched, closure of the switches 94n after movement of the cam shaft 93 by the dog ||2 is prevented thereby maintaining the rapid traverse motor deenergized as the feed motor continues to operate. The latch is arranged to be tripped by axial shifting of a rod |60 slidable in the block |63 and having one end positioned adjacent an arm |8| on the latch and the other end projecting from the block.

In the step of the cam shaft movement which is produced by the dog ||2 as the tool head approaches the stop |55, the mechanism for timing the dwell period is set in operation. This mechanism includes a sleeve |6| having clutch teeth |62 thereon and rotatably supported in a bearing block |63 on the frame 89. The sleeve has worm teeth meshing with a worm |64 on a shaft |65 which is driven from the vertical shaft 16 through the medium of spiral gears |66 which can be changed to vary the speed at which the sleeve itl rotates during operation of the feed motor 45.

Extending through the sleeve i5! is a rod |68 having loose thereon a disk it@ engaging a flange i695 and carrying clutch teeth |10 urged toward the teeth |62 by a spring lli acting between the sleeve and a nut i12 on the rod. A collar |13 surrounding the sleeve iiiE is adapted for angular adjustment but is normally locked to the block |63 by a set screw |14. This collar has a recess extending parallel to the clutch axis and has a slidable plunger |15 which is urged toward the disk |69 by a c ompression spring |16 stronger than the spring |1|. In the stopped position of the disk shown in Fig. 1l, the plunger |15 engages a projection |11 on the disk so that the spring |16 holds the clutch disengaged. 'Ihe projection is of sufficient radial length to engage the trip rod as well as the plunger |15.

In the movement of the cam shaft 93 caused by the dog ||2 as the tool head approaches the stop |55, a lobe |18 on a cam |19 carried by the cam shaft is moved into engagement with the end |83 of the rod |68 shifting the disk against the action of the spring |16 and causing engagement of the teeth |10 with the rotating teeth |62. The disk is thus rotated by the feed motor, engagement of the clutch being maintained by the spring |1|. After turning through an angle determined by the starting position of the disk, the projection |11 engages the rod |60 and shifts the same to trip the latch |51. This releases the follower tails |56 permitting closure of the switches 94* and initiating rapid return of the tool head to starting position in the manner previously described. However, the disk continues to rotate until, after the cam shaft 93 has been advanced by the dog to render the cam lobe |16 ineffective, the projection |11 rides up on the inclined end of the plunger |15 which, owing to the strength of the spring |16, shifts the disk axially to release the clutch. The disk is thus stopped in a position which is determined by the angular position of the collar |13 and may be varied as desired to obtain different dwell periods.

When the spot facing control is not in use, the cam shaft 93 is shifted axially to move the cam |19 out of engaging relation with respect to the follower rod |60. Also the trip rod |80 is shifted to the right as viewed in Fig. ll and held by a set screw |83 in a position such as to maintain the latch |8| ineective in holding the follower tails |56.

The tool head actuating mechanism although described above in considerable detail, is typical of the various mechanisms which may be employed for rotating the tool spindle and feeding the head along the supporting guide rods. Obviously, other types of coacting feed elements, herein illustrated as the nut 61 and the screw 69 are contemplated as well as actuating mechanisms suited for actuation of the particular feed elements employed.

I claim as my invention:

l. A machine tool having, in combination. a tool head having at least one rotary spindle projecting therefrom for driving a tool to operate upon a work piece, a prime mover mounted on said head and having a driving connection extending to said spindle, there being a lplurality of open ended parallel bores on said head extending parallel to the axes of said spindle and providing internal cylindrical way surfaces, a rigid box-like fixture i frame having a base and upstanding side portions rigidly connected at their upper ends, said fixture being arranged to support said work piece in a position to be operated upon, means providing a cantilever mounting for supporting said tool head solely from said fixture frame comprising a'plurality of elongated rods rigidly attached at one of their ends to said fixture frame and projecting in spaced parallel relation away from the frame with their axes spaced to coincide with the axes of said bores, the pe- 'J5 ripheral surfaces of said rods constituting cylindrical slideways snugly received in said bores, and means for reciprocating said tool head along said rods including power driven mechanism arranged to apply an actuating force to said head along a line disposed substantially in a plane including the axes of said rods.

2. A machine tool having, in combination, a tool head having at least one rotary spindle projecting therefrom for driving a tool to operate upon a work piece, a prime mover mounted on said head and having a driving connection extending to said spindle, there being a plurality of open ended parallel bores on said head extending parallel to the axes of said spindle and providing internal cylindrical way surfaces, a rigid box-like fixture frame having a base and upstanding side portions rigidly connected at their upper ends, said fixture being arranged to support said work piece in a position to be operated upon, means providing a cantilever mounting for supporting said tool head solely from said xture frame comprising a plurality of elongated rods rigidly attached at one of their ends to said fixture frame and projecting in spaced parallel relation away from the frame with their axes spaced to coincide with the axes of said bores, the peripheral surfaces of said rods constituting cylindrical slideways snugly received in said bores and slidably supporting said head, and power actuated means for reciprocating said tool head along said rods.

3. A machine tool having, in combination, a tool head having at least one rotary spindle projecting therefrom; for driving a tool to operate upon a work piece, a prime mover mounted on said head and having a driving connection extending to said spindle, a plurality of internal way surfaces on said head extending parallel to the axes of said spindle, a rigid box-like fixture frame arranged to support said work piece in a position to be operated upon, means providing a cantilever mounting for supporting said tool head solely from said fixture frame comprising a plurality of elongated rods rigidly attached at one of their ends to said xture frame and projecting in spaced parallel relation therefrom, the external surfaces of said rods constituting slideways mating with said way surfaces whereby to slidably support said head, and power actuated means for reciprocating said tool head along said rods.

4. A machine tool having, in combination, a tool head having at least one rotary spindle projecting therefrom for driving a tool to operate on a work piece, a plurality of internal way surfaces on said head extending parallel to the direction of feed of the spindle, a support adapted to rest upon the floor and providing a heavy rigid fixture frame for supporting and holding a work piece in elevated position to be operated upon, a plurality of rods rigidly attached at one of their ends to said xture frame and projecting in spaced parallel relation therefrom, the external surfaces of said rods constituting slideways mating with and enclosed by said way surfaces so that said head is primarily supported from said fixture frame through the medium of said rods during active engagement of the tool and work piece, relatively movable coacting feed elements having their axes extending parallel to and disposed substantially in the plane of said rods, one of said elements being rigidly mounted relative to said rods and the other element being mounted on the head' to travel therewith, a prime mover on said head for rotating said spindle, and power actuated means for operating the movable feed element to move said head along said rods.

5. A machine tool having, in combination, a tool head having at least one rotary -spindle projecting therefrom for driving a tool to operate on a work piece, a plurality of internal Way surfaces on said head extending parallel to the direction of feed of the spindle, a support adapted to rest upon the floor and providing a heavy rigid fixture frame for supporting a work piece in elevated position to be operated upon, a plurality of rods rigidly attached at one of their ends to said fixture frame and projecting in spaced parallel relation therefrom, the external surfaces of said rods constituting slideways mating with and enclosed by said way surfaces so that said head is primarily supported from said fixture frame through the medium of said rods during active engagement of the tool and work piece, relatively movable coacting feed elements having their axes extending parallel to and disposed substantially in the plane of said rods, one of said elements being rigidly connected to said fixture frame adjacent the point of attachment of said rods thereto, and a prime mover carried by and movable with said head and having connections for transmitting power to said spindle -for rotating the latter and also to said movable feed element to cause movement of said head along said rods.

ALEXANDER OBERHOFFKEN; 

